Long-term Efficacy of the Mass Deacidification of Library Materials

Objective

Most papers which were manufactured between the industrialisation of the paper-making process (i.e. roughly 1850) and 1980 contain lignin-based fibres from the mechanical wood pulp and acid substances which were used in the sizing process. In consequence the paper lost its stability over time, becoming brown and brittle and eventually unusable. Ever since the 1990s libraries and archives have therefore been deploying deacidification methods. The treatment aims to improve the durability of the paper by neutralising any existing acid and depositing an alkaline reserve. It is not possible, however, to determine whether paper has been successfully neutralised from its appearance or its texture.

The "Long-term Efficacy of the Mass Deacidification of Library Materials" project evaluated the lasting effect of the mass deacidification on the basis of scientific examinations. The tests were performed on the holdings of the German National Library in Leipzig and the Staatsbibliothek zu Berlin - Preußischer Kulturbesitz which were neutralised from 1994 to 2006 and from 1998 to 2006 respectively. The chemical analyses were carried out by the Department of Chemistry at the University of Natural Resources and Life Sciences in Vienna. The pH value and the alkaline reserve were tested, as was the long-term effect on the neutralised paper using an artificial ageing process. One of the project's key findings is that the lower the level of damage before the start of treatment, the greater the effect of the deacidification process. In ideal circumstances, deacidification can slow down the decay of the paper by a factor of roughly three. However, it is impossible to arrest the process completely.

This therefore gives the deacidification institutions an important decision-making tool regarding the economical use of long-term preservation techniques for library and archive materials. In future, the selection of books for deacidification should be further optimised in order to maximise the effect of the work. The project itself has highlighted the great significance of the application and the importance of developing binding standards for quality controls.